1. Field of the Invention
The present invention relates to an image forming apparatus and an image reader, such as a copy machine and a multifunctional peripheral, and particularly to operation control performed based on a pattern for prohibiting the copying or reading of a document when the pattern is detected.
2. Description of the Related Art
There have conventionally been various technologies for preventing or inhibiting the copying or duplication of a confidential document that needs to be kept confidential, such as data containing classified information of a company, and for preventing or inhibiting the use of a copied material thereof. One of the technologies is a tint block print technology for embedding, in the image of a document, a tint block that has the background composed of a certain number of screen lines and a latent image part composed of screen lines the number of which is higher than that of the abovementioned screen lines (halftone dot density).
For example, according to a known technology of this kind, if a document image created by this tint block print technology is copied, area corresponding to the latent image embedded in the document image becomes white in the copy, so that patterns such as “copy prohibited” emerges visibly. With this technology, copying of a document can be psychologically restricted or inhibited.
However, this conventional technology merely restricts or inhibits the copying of a document psychologically, and is not capable of stopping a foul conduct of copying itself.
For the purpose of restricting such a foul conduct, there is proposed a technology for reading the image of a document, detecting a special dot pattern embedded in a background image that is contained in image data obtained by the reading operation, comparing the detected special dot pattern with a special dot pattern stored in advance, and prohibiting an action of forming the image on a piece of paper when the both special dot patterns match.
However, according to this conventional technology, the control for prohibiting the action of forming the image on a piece of paper and control for allowing the action are switched only in accordance with whether or not a predetermined special dot pattern exists or not. Therefore, it cannot perform advanced control such as a control of allowing a predetermined user to obtain a copy even if the special dot pattern is determined, a control of allowing use of limited function such as allowing only black-and-white copying out of color copying or black-and-white copying, or a control of allowing only low-resolution scanning out of high-resolution scanning or low-resolution scanning.
Furthermore, an image forming apparatus performing the following control is proposed. Specifically, the image forming apparatus carries out a series of control described below. That is, (1) in order to improve a fixed form that cannot allow an advance control operation to be performed, such as allowing a specific user to perform copying depending on the document or allowing copying to be performed after a predetermined date, this image forming apparatus (2) stores duplication prohibiting information, which indicates that a document instructed to be printed out is prevented from being duplicated by a copy machine (prohibiting the duplication), and condition information (including a password, a user ID number (staff number etc.) allowing the duplication, a date when the prohibition of the duplication is lifted, and a machine number of the copy machine allowing the duplication), which indicates a condition for enabling duplication of the document instructed to be printed out, (3) has a pattern image storage unit for storing a pattern image shown by a plurality of types of dot patterns corresponding to code data obtained by encoding the duplication prohibition information or the condition information, and (4) when a document image read by an image reader contains a pattern image showing a duplication-prohibited code during a “normal copy mode,” a duplication prohibition information detection unit detects that the pattern image is contained, thereby prohibiting a duplication operation. On the other hand, when the pattern image showing the duplication-prohibited code is not contained, the duplication prohibition information detection unit enables a normal duplication operation for printing out the read image onto a piece of paper. (5) When the document image read by the image reader contains a pattern image showing a condition code during a “conditional copy mode,” a condition information detection unit detects that the pattern image is contained, and allows the duplication operation to be performed only when the condition matches a predetermined condition that is registered in advance. When, on the other hand, the pattern image showing the condition code is not contained, the condition information detection unit enables the normal duplication operation for printing out the read image onto a piece of paper.